1. Field of the Invention
Transfer lines for machining workpieces, e.g. for the chip-removing machining of housings or the like, are often equipped with a so-called return line. This return line has the purpose of taking the workpiece-carriers, at the end of the transfer line, and carrying them back to the entry into the transfer line. Along this return line the workpieces may for their part pass again through treatment stations, in which for example the workpieces are cleaned of chips and adherent coolant or lubricant.
2. Description of the Prior Art
With the transfer lines known in practice the arrangement is such that the individual workpiece-carriers, at the end of the transfer line, are for example pushed at a transfer station by hydraulic piston drives or chain conveyors at right angles to their former direction of conveyance and onto the slideway of the return line, after which they are pushed along the slideway as far as the first corner of the return line. There the work carriers, while retaining their spatial orientation, are taken over, again for example by hydraulic pushing mechanisms or chain conveyors, which push the workpiece-carriers onward along the slideway, substantially parallel to the intermittently-moved line, until they reach the second corner. At this second corner the workpiece-carriers, again retaining their spatial orientation, are taken over by a new pushing mechanism, which brings them back by a 90.degree. turn to the entry into the transfer line. This method of returning the workpiece-carriers requires that the individual workpiece-carriers, at both corners of the U-shaped return line must in each case be brought to a standstill, and then accelerated again at right angles to their previous direction of movement by conveying mechanism. It is thereby inevitable that the workpiece-carriers are subjected to a substantial acceleration forces, which in the case of certain workpieces brings a risk of tipping the workpiece-carrier. There is moreover a certain difficulty in braking the workpiece-carriers at their arrival at the corners of the return line, because the workpiece-carriers being pushed ahead become detached, under too rapid a braking, from their conveying element, and run away in the direction of conveyance. Furthermore, such a return line, where use is not made of square workpiece-carriers, requires slideways of different widths for the parts located between the corner-points, because the workpiece-carriers at the corners in each case retain their spatial orientation, which means that with workpiece-carriers which are not square a workpiece-carrier has to be moved endways and then sideways, or vice versa.